1. Field of the Invention
The present invention relates to a novel human defensin peptide. More specifically, isolated nucleic acid molecules are provided encoding a human antimicrobial peptide. Antimicrobial polypeptides are also provided, as are vectors, host cells and recombinant methods for producing the same. Also provided are diagnostic methods for detecting disorders related to the immune system and therapeutic methods for treating such disorders.
2. Related Art
One of the key roles of the respiratory epithelium in mammals is to form a barrier to potentially harmful environmental threats. A number of defense mechanisms have been identified that protect the respiratory tract from airborne agents that are thought to be responsible for airway disease, such as infectious agents, gases and particulates. (Newhouse et al., xe2x80x9cRespiratory Tract Defense Mechanismxe2x80x9d Textbook of pulmonary Disease, Little Brown and Co. (1989)). The recent identification and characterization of antimicrobial peptides from a variety of species has unveiled a new member of the animal host defense system and are believed to participate in the defense against potential microbial pathogens. These newly identified antimicrobial peptides families include cecropins, magainins, and defensins. Cecropins were the first well-characterized family of structurally related antimicrobial polypeptides and are found in a wide distribution of insects. (Bowman et al., Ann. Rev. of Microbiol. 41:103 (1987)). In vertebrates, the magainin family of antimicrobial peptides have been isolated from the glands of the skin and gastrointestinal tract of Xenopus laevis, and are thought to form the basis for defense system of the amphibian mucosal surfaces against infection. (Soravia et al., FEBS Lett. 228:337 (1988); Zasloff et al., Proc. Natl. Acad. Sci. 84:5449 (1987)). Defensins are antimicrobial peptides found in phagocytic cells isolated from several mammalian species including man and may be characterized by eight invariant residues within the sequence. (Gabay et al., Curr. Opin. Immunol. 1: 36 (1988); Gabay et al., Proc. Natl. Acad. Sci. 86:5610 (1989); Ganz et al., Infect. Immun. 55:568 (1987); Ganz et al., J. Immunol. 143:1358 (1989); Ganz et al., J. Clin. Invest. 76:1427 (1985)).
The mechanism of antimicrobial activity of peptides such as the defensins is via a selective membrane disruption leading to a characteristic broad spectrum of antibiotic activity. (Bowman, Ann. Rev. of Immunol. 13:61 (1995)). The antimicrobial spectrum of defensins includes gram positive and gram negative bacteria, mycobacteria, T. pallidum, many fuigi, some enveloped-viruses. (Bowman, Ann. Rev. of Immunol. 13:61 (1995)). Defensins exert nonspecific cytotoxic activity against a wide range of normal and malignant targets, including cells resistant to TNF-xcex1 and NK-cytolytic factor. They appear to kill mammalian target cells and microorganisms by common mechanism which involves initial electrostatic interactions with negatively charged target cell surface molecules, followed by insertion into the cell membranes which they permeabilize, forming voltage regulated channels. (Lehrer et al., Ann. Rev. of Immunol. 11:105 (1993)). In addition to their antimicrobial and cytotoxic properties, some defensins act as opsonins, while others inhibit protein kinase C, bind specifically to the ACTH receptor and block steroidogenesis or act as selective chemoattractins for monocytes. Defensins are newly delineated family of effector molecules whose contribution to host cell defense, inflammation, and cytotoxicity may be considerable for humans. (Lehrer et al., Ann. Rev. of Immunol. 11:105 (1993)). Defensins are basic peptides 30-34 amino acids with three disulfide bonds. The known characterized defensins for both myeloid and nonmyeloid tissues all have highly conserved amino acid residues within the family, including 6 invariant cysteins. Recent studies have found that similar antimicrobial peptides are also made by certain epithelial cells suggesting an additional role in the defense of mucosal surfaces. (Diamond et al., Proc. Natl. Acad. Sci. 90:5496 (1993); Diamond et al., Proc. Natl. Acad. Sci. 88:3952 (1991); Eisenhauer et al., Infect. Immun. 60:3556 (1992); Jones et al., J. Biol. Chem. 267:23216 (1992); Schonwetter et al., Science 267:1645 (1995); Selsted et al., J. Cell. Biol. 118:929 (1992)).
Tracheal antimicrobial peptide (TAP) is a 38 amino acid peptide isolated from the bovine respiratory mucosa and was the first member of what is now recognized as a relatively large family of antimicrobial peptides, xcex2-defensin, all of which have broad spectrum antimicrobial activity in vitro. (Diamond et al, Proc. Natl. Acad. Sci. 88:3952 (1991)). Recently a second xcex2-defensins of epithelial origin, lingual antimicrobial peptide (LAP) was isolated from bovine tongue. (Schonwetter et al., Science 267:1645 (1995); Selsted et al., J. Cell. Biol. 118:929 (1992)).
Thus, there is a need for polypeptides that function as antimicrobial or immune regulators, since disturbances of such regulation may be involved in disorders relating to infectious diseases, inflammation and immune disorders.
The present invention provides isolated nucleic acid molecules comprising a polynucleotide encoding the antimicrobial polypeptide having the amino acid sequence shown in SEQ ID NO:2 or the amino acid sequence encoded by the cDNA clone deposited as ATCC Deposit Number 97982 on Apr. 14, 1997.
The present invention also relates to recombinant vectors, which include the isolated nucleic acid molecules of the present invention, and to host cells containing the recombinant vectors, as well as to methods of making such vectors and host cells and for using them for production of antimicrobial polypeptides or peptides by recombinant techniques.
The invention further provides an isolated human antimicrobial polypeptide having an amino acid sequence encoded by a polynucleotide described herein.
The invention provides a diagnostic method useful during diagnosis of immune system disorders.
An additional aspect of the invention is related to a method for treating an individual in need of an increased level of antimicrobial peptide activity in the body comprising administering to such an individual a composition comprising a therapeutically effective amount of an isolated antimicrobial peptide of the invention or an agonist thereof.
A still further aspect of the invention is related to a method for treating an individual in need of a decreased level of antimicrobial peptide activity in the body comprising, administering to such an individual a composition comprising a therapeutically effective amount of an antimicrobial peptide antagonist.